The present invention relates to a projection aligner for projecting a pattern formed on a mask onto an object to be exposed to transfer the pattern to the object.
Projection aligners have been used to form wiring patterns of PCBs (Printed Circuit Boards), transparent electrodes of LCD (Liquid Crystal Display) panels and the like. In such projection aligners, a light beam is emitted from a high-power light source, such as an ultra-high-pressure mercury-vapor lamp, toward the object through the mask.
Objects such as printed circuit boards expand/contract in size up to 0.2% due to temperature variation of the atmosphere and/or forces applied thereon during surface polishing process and/or laminating process thereof. To transfer the image of the mask pattern to the object at a correct location irrespective the expansion/contraction of the object, the projection aligners enlarge/reduce the image of the mask pattern in accordance with the expansion/contraction of the object.
There are projection aligners that scans a plurality of light beams across the mask and the object in a predetermined scanning direction to transfer the entire pattern of a large size mask to the object. If the image is enlarged or reduced in accordance with the expansion/contraction of the object in such kind of projection aligners, the images formed on the object by the plurality of light beams become to be overlapped or to be spaced apart to each other in a direction perpendicular to the scanning direction and the image cannot be transferred correctly to the object.